The mechanisms of changes in the starch inner-structures of germinated parboiled rice: the role of processing

Rice processing profoundly alters starch structure, thereby influencing its quality and nutritional properties. This study systematically elucidated how germination and parboiling reshaped the multi-scale structure of rice starch using multiple detection techniques. Germination slightly reduced short-range order, relative crystallinity (RC), double-helix structure and crystalline layer thickness while parboiling caused more significant reductions. Their combination synergistically enhanced V-type crystallinity (15.45 ± 0.82%) and single-helix content (28.88 ± 1.68%) in germinated parboiled rice (GPR). Structural changes strongly correlated with functional properties. Increased gelatinization temperatures and resistant starch (RS) content, alongside decreased gelatinization enthalpy (ΔH) and pasting viscosity. Germination disrupted granule surface order, facilitating molecular rearrangement during parboiling, and subsequent cooling enhanced short-range order and crystallinity despite some molecular aggregation. These findings demonstrate how sequential processing can be tailored to design rice-based foods with modulated digestibility, offering a potential staple option for individuals with gastrointestinal sensitivities.